The present invention relates to a developer-carrying member for developing a latent image formed on a latent image-bearing member to form a toner image in electrophotography, electrostatic recording or magnetic recording. More specifically, the present invention relates to a method for regeneration of such a developer-carrying member, a regenerated developer-carrying member and a developing device including such a regenerated developer-carrying member.
Many electrographic methods have been known heretofore. Generally, an electrical latent image is formed on an electrostatic latent image-bearing member (photosensitive member) comprising a photoconductor material by various means, and is developed with a toner (developer) to form a toner image (visible image), which is then transferred onto a transfer(-receiving) material, such as paper, as desired, and then fixed onto the transfer material by application of heat, pressure, or heat and pressure to form a copy or a print. In recent years, printers and facsimile apparatus are popularly formed as machines using electrophotography in addition to conventional copying machines. The developing schemes are roughly divided into the two-component developing scheme using carrier particles and the mono-component developing scheme not using such carrier particles. The mono-component developing schemes include the magnetic mono-component developing scheme wherein a developer comprising toner particles containing magnetic powder is conveyed under the action of a magnetic force, and the non-magnetic monocomponent developing scheme wherein a developer containing no magnetic powder is carried on a developer-carrying member under the action of a triboelectric charge. In the magnetic mono-component developing scheme, the magnetic material may be used also as a colorant, without using a colorant such as carbon black.
In the two-component developing scheme, carrier particles such as glass beads or iron powder are necessary, and a device for detecting a toner concentration to replenish a necessary amount of toner is necessary for maintaining a constant toner concentration in the developer, so that the entire developing device tends to be large and heavy. In the two-component developing scheme, the toner component is liable to be attached onto the carrier, thus causing a spent carrier, so that it becomes necessary to exchange the carrier. In the mono-component developing scheme, such a carrier or related device is not required, so that the entire developing device can be made smaller and lighter, and the maintenance operation is not required for a long period since carrier exchange is not required. Because of necessity of the magnetic powder, in the magnetic mono-component developing scheme, it becomes difficult to effect clear color toner formation, whereas the two-component developing scheme is preferably used for color development since the developing state can be finely controlled by the density detection device.
As for printer devices, LED printers and LBP printers become predominant in the market, and high resolutions (e.g., 600, 800 and 1200 dpi) are being required. Accordingly, a developing scheme achieving a high resolution is required. Further, a digital machine is becoming predominant for also copying machines, and is made appliable to multi-functional use so as to be also usable as a facsimile apparatus or a printer, so that the difference between a copying machine and a printer is becoming less. A high-resolution and high-definition developing scheme is also required in multi-function machines. For example, Japanese Laid-Open Patent Application (JP-A) 1-112253 and JP-A 2-284158 have proposed to use a small-particle size toner, and toners having central particle sizes of ca. 5-9 xcexcm are becoming predominant as high resolution is required.
The developer-carrying member used in the above-mentioned developing schemes has been conventionally formed by shaping, e.g., a metal, alloy or a compound, into a cylinder, and treating the surface thereof by electrolysis, blasting or filing so as to provide a prescribed surface roughness. A portion of developer present close to the surface of such a developer-carrying member in a developer layer formed on the developer-carrying member by a regulating member is liable to have a very high charge and therefore attracted to the developer-carrying member surface by a strong image force. In such a case, an upper layer of toner is not provided with a sufficient opportunity of triboelectrification, thus being liable to have an insufficient charge. Under such circumstances, sufficient development and transfer cannot be achieved, thus being liable to result in images accompanied with image density irregularity and scattering of character images.
In order to prevent the occurrence of such a developer having an excessive charge or strong attachment of the developer, it has been proposed to form a film of a resin containing an electroconductive substance such as carbon graphite or a solid lubricant such as graphite disposed therein on the developer-carrying member in, e.g., JP-A 01-277265, JP-A 05-006089, and JP-A 05-066680.
Such a developer-carrying member heaving a resinous coating layer, when used in a process cartridge, is used up to the consumption of the developer in the cartridge, or when used in a developing device operated by replenishing a developer as desired, is used up to the end of the life of the developing device, in a copying machine, a printer or a facsimile apparatus including such a process cartridge or a developing device. Accordingly, a thermosetting type resin having a good wear resistance has been preferably used as the resin for binding the electroconductive fine particles or the solid lubricant.
On the other hand, in order to retain a suitable level of toner conveying performance on a developer-carrying member (also called a developing sleeve), the developer-carrying member surface is required to have an appropriate degree of surface roughness. Accordingly, the resinous coating layer surface is intentionally roughened to adjust a developer-carrying amount.
However, in view of a long period of continual use, it is difficult to prevent the change in surface roughness, and the developer carrying amount is inevitably changed correspondingly. Further, along with the surface roughness change, the developer-carrying member is liable to be soiled with deteriorated developer. Accordingly, a developer-carrying member used throughout the life of a cartridge or a developing device is difficult to satisfy image forming performances attained at its initial use, and has been disposed simultaneously at the end of the life of the cartridge or the developing device.
In recent years, however, the reduction of waste product is becoming an urgent matter, and the re-utilization of even a functional material for electrophotography, such as a developer-carrying member, is required. For example, it has been proposed to remove the resinous layer on the. developer-carrying member surface by a cutting means, such as a cutting bite and re-apply a surface processing, such as blasting or resin coating, similarly as on a fresh tube. However, the resin layer removal by bite cutting is accompanied with a difficulty that a surface resin layer is very difficult to cut. More specifically, the resin is liable to be attached onto a cutting bite to fail in uniform cutting, and the bite has to be exchanged at a very high frequency. Further, the use of a grindstone has also been proposed, but the grinding therewith is hindered by stopping-up with the resin. Several proposals have been made of blasting for removal of such a surface resin layer on a developer-carrying member. For example, JP-A 08-171724 has disclosed to remove a surface resin layer by blasting after removing the flange of a developing roller. Further, JP-A 11-174891 has also disclosed that it is possible to peel off a resinous surface coating layer by blasting or grinding. However, a detailed method thereof is not disclosed. The removal of a resinous coating layer by blasting is accompanied with several problems.
Hitherto, it has been known to use a hollow or solid cylinder of aluminum, stainless steel, brass or shaped resin, as a substrate of a developer-carrying member. Such a substrate is used after processing at a high accuracy so as to obtain high-quality image through an electrophotographic developing method.
For example, in a jumping developing method wherein a latent image-bearing member and a developer-carrying member are disposed with a prescribed gap therebetween, and a developer is formed in a layer at a thickness smaller than the gap and is used to develop a latent image formed on the image-bearing member while applying a developing bias voltage between the image-bearing member and the developer-carrying member, it is difficult to obtain uniform images unless the constant gap is retained between the latent image-bearing member and the developer-carrying member. For example, if a constant gap is not retained between the image-bearing member and the developer-carrying member, thereby resulting in a substantial fluctuation in gap during a rotation of the developer-carrying member relative to a vertical surface, there are encountered image defects, such as pitch irregularity or periodical density irregularity in solid black or halftone images, line width irregularity of line images or developer scattering around character images. Such a gap fluctuation should be suppressed to at most 30 xcexcm ordinarily, and at most 15 xcexcm for a laser beam printer or a digital machine for reproducing a high-definition graphic image. Among substrate materials usable for the developer-carrying member substrate, aluminum is suitably used because of lightness and high-accuracy processability.
However, in the case of removing a resin coating formed on an aluminum substrate by blasting, the following problems are liable to occur. Blasting with too strong a force results in deformation of the aluminum substrate to provide a larger gap fluctuation after the blasting than the original substrate. When a regenerated developer-carrying member is produced by using such a regenerated substrate and is used in a developing device, the above-mentioned image defects of pitch irregularity, line-width irregularity and scattering are liable to occur. Further, as too large a surface roughness occurs after the resin coating layer removal by blasting, it becomes difficult to form a resin coating layer surface having a uniform and suitable surface roughness thereon for regeneration, thus being liable to cause peeling-off or a lowering in surface roughness of the resins coating layer. This also adversely affects the image uniformity. On the other hand, too low a blasting force fails in removal of the resin coating layer as the resin coating layer inherently has a certain wear resistance.
As a method of removing such a resin coating layer other than the blasting mentioned above, a method of dissolving the resin coating layer with an organic solvent has been proposed as disclosed in JP-A 10-031367. The JP-reference particularly discloses the use of a mixture of water and a water-immiscible solvent having a larger specific gravity than water for dissolving and peeling the resin coating layer in order to prevent the evaporation of the organic solvent. According to this method, it is possible to dissolve and peel the coating layer to some extent, but this becomes difficult in the case of a large layer thickness or depending on a resin constituting the coating layer. Particularly, in the case of a coating layer of a thermosetting resin, it is difficult to find an organic solvent having a high dissolving power to the resin to allow the peeling of the resin layer in many cases.
As another method, a method of wiping and removing a resin coating layer with a fibrous material, such as cloth or felt, as disclosed in JP-A 08-036341. According to this method, however, it is only possible to apply a wiping force capable of removing toner affixed and remaining on the resin coating layer on a used developer-carrying member, and it is insufficient to abrade and peel the resin coating layer.
Accordingly, a method of regenerating a developer-carrying member is desired for providing a regenerated developer-carrying member free from difficulties in image formation, such as image defects as mentioned above, and for suppressing the amounts of waste materials.
An object of the present invention is to provide a method of regenerating a developer-carrying member and a regenerated developer-carrying member capable of providing high-definition images free from pitch irregularity, line-width irregularity, scattering, and further, blotch, ghost or fog.
Another object of the present invention is to provide a method of regenerating a developer-carrying member and a regenerated developer-carrying member capable of peeling or abrasion of a resin coating layer on the surface and capable of retaining high-definition images even after a long period of use.
A more specific object of the present invention is to provide a method of removing a surface resin coating layer on a developer-carrying member so as not to cause inadequacy regarding gap fluctuation or surface roughness and forming a fresh resin coating layer thereon to provide a regenerated developer-carrying member capable of providing high-definition images comparable to those obtained by a fresh developer-carrying member.
A further object of the present intention is to provide a developing device including such a regenerated developer-carrying member.
A still further object of the present invention is to provide a method capable of reducing waste materials and reducing the costs for Introduction of a developer-carrying member and a developing device.
According to the present invention, there is provided a method of regenerating a used developer-carrying member having a resin coating layer on a substrate, comprising:
scraping the resin coating layer of the used developer-carrying member to form a developer-carrying member surface having unevenness showing a (central line-average roughness Ra of at most 0.8 xcexcm and
coating the developer-carrying member surface having the unevenness with a coating layer of a resinous composition comprising at least a binder and electroconductive fine powder.
The present invention further provides a regenerated developer-carrying member obtained through the above-mentioned method, and also a developing apparatus including such a regenerated developer-carrying member.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.